'\" te
.\"  Copyright 2014 Garrett D'Amore <garrett@damore.org>
.\"  Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH DDI_DMAE 9F "Jan 18, 2020"
.SH NAME
ddi_dmae, ddi_dmae_alloc, ddi_dmae_release, ddi_dmae_prog, ddi_dmae_disable,
ddi_dmae_enable, ddi_dmae_stop, ddi_dmae_getcnt, ddi_dmae_1stparty,
ddi_dmae_getattr \- system DMA engine functions
.SH SYNOPSIS
.nf
\fBint\fR \fBddi_dmae_alloc\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR, \fBint (*\fR\fIcallback\fR) (caddr_t),
     \fBcaddr_t\fR \fIarg\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_release\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_prog\fR(\fBdev_info_t *\fR\fIdip\fR, \fBstruct ddi_dmae_req *\fR\fIdmaereqp\fR,
     \fBddi_dma_cookie_t *\fR\fIcookiep\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_disable\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_enable\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_stop\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_getcnt\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR, \fBint *\fR\fIcountp\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_1stparty\fR(\fBdev_info_t *\fR\fIdip\fR, \fBint\fR \fIchnl\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_dmae_getattr\fR(\fBdev_info_t *\fR\fIdip\fR, \fBddi_dma_attr_t *\fR\fIattrp\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIdip\fR\fR
.ad
.RS 12n
A \fBdev_info\fR pointer that identifies the device.
.RE

.sp
.ne 2
.na
\fB\fIchnl\fR\fR
.ad
.RS 12n
A \fBDMA\fR channel number. On \fBISA\fR buses this number must be \fB0\fR,
\fB1\fR, \fB2\fR, \fB3\fR, \fB5\fR, \fB6\fR, or \fB7\fR.
.RE

.sp
.ne 2
.na
\fB\fIcallback\fR\fR
.ad
.RS 12n
The address of a function to call back later if resources are not currently
available. The following special function addresses may also be used:
.sp
.ne 2
.na
\fB\fBDDI_DMA_SLEEP\fR\fR
.ad
.RS 20n
Wait until resources are available.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_DONTWAIT\fR\fR
.ad
.RS 20n
Do not wait until resources are available and do not schedule a callback.
.RE

.RE

.sp
.ne 2
.na
\fB\fIarg\fR\fR
.ad
.RS 12n
Argument to be passed to the callback function, if specified.
.RE

.sp
.ne 2
.na
\fB\fIdmaereqp\fR\fR
.ad
.RS 12n
A pointer to a \fBDMA\fR engine request structure. See \fBddi_dmae_req\fR(9S).
.RE

.sp
.ne 2
.na
\fB\fIcookiep\fR\fR
.ad
.RS 12n
A pointer to a \fBddi_dma_cookie\fR(9S) object,
which contains the address and count.
.RE

.sp
.ne 2
.na
\fB\fIcountp\fR\fR
.ad
.RS 12n
A pointer to an integer that will receive the count of the number of bytes not
yet transferred upon completion of a \fBDMA\fR operation.
.RE

.sp
.ne 2
.na
\fB\fIattrp\fR\fR
.ad
.RS 12n
A pointer to a \fBDMA \fR attribute structure. See \fBddi_dma_attr\fR(9S).
.RE

.SH DESCRIPTION
There are three possible ways that a device can perform \fBDMA\fR engine
functions:
.sp
.ne 2
.na
\fBBus master DMA\fR
.ad
.RS 19n
If the device is capable of acting as a true bus master, then the driver should
program the device's \fBDMA\fR registers directly and not make use of the
\fBDMA\fR engine functions described here. The driver should obtain the
\fBDMA\fR address and count from \fBddi_dma_cookie\fR(9S).
.RE

.sp
.ne 2
.na
\fBThird-party \fBDMA\fR\fR
.ad
.RS 19n
This method uses the system \fBDMA\fR engine that is resident on the main
system board. In this model, the device cooperates with the system's \fBDMA\fR
engine to effect the data transfers between the device and memory. The driver
uses the functions documented here, except \fBddi_dmae_1stparty()\fR, to
initialize and program the \fBDMA\fR engine. For each \fBDMA\fR data transfer,
the driver programs the \fBDMA\fR engine and then gives the device  a command
to initiate the transfer in cooperation with that engine.
.RE

.sp
.ne 2
.na
\fBFirst-party DMA\fR
.ad
.RS 19n
Using this method, the device uses its own \fBDMA\fR bus cycles, but requires a
channel from the system's \fBDMA\fR engine. After allocating the \fBDMA\fR
channel, the \fBddi_dmae_1stparty()\fR function may be used to perform whatever
configuration is necessary to enable this mode.
.RE

.SS "\fBddi_dmae_alloc()\fR"
The \fBddi_dmae_alloc()\fR function is used to acquire a \fBDMA\fR channel of
the system \fBDMA\fR engine. \fBddi_dmae_alloc()\fR allows only one device at a
time to have a particular \fBDMA\fR channel allocated. It must be called prior
to any other system  \fBDMA\fR engine function on a channel. If the device
allows the channel to be shared with other devices, it must be freed using
\fBddi_dmae_release()\fR after completion of the \fBDMA\fR operation. In any
case, the channel must be released before the driver successfully detaches. See
\fBdetach\fR(9E). No other driver may acquire the \fBDMA\fR channel until it is
released.
.sp
.LP
If the requested channel is not immediately available, the value of
\fIcallback\fR determines what action will be taken. If the value of
\fIcallback\fR is \fBDDI_DMA_DONTWAIT\fR, \fBddi_dmae_alloc()\fR will return
immediately. The value \fBDDI_DMA_SLEEP\fR will cause the thread to sleep and
not return until the channel has been acquired. Any other value is assumed to
be a callback function address. In that case, \fBddi_dmae_alloc()\fR returns
immediately, and when resources might have become available, the callback
function is called (with the argument \fIarg\fR) from interrupt context. When
the callback function is called, it should attempt to allocate the \fBDMA\fR
channel again. If it succeeds or no longer needs the channel, it must return
the value \fBDDI_DMA_CALLBACK_DONE\fR. If it tries to allocate the channel but
fails to do so, it must return the value \fBDDI_DMA_CALLBACK_RUNOUT\fR. In this
case, the callback function is put back on a list to be called again later.
.SS "\fBddi_dmae_prog()\fR"
The \fBddi_dmae_prog()\fR function programs the \fBDMA\fR channel for a
\fBDMA\fR transfer. The \fBddi_dmae_req\fR structure contains all the
information necessary to set up the channel, except for the memory address and
count. Once the channel has been programmed, subsequent calls to
\fBddi_dmae_prog()\fR may specify a value of \fINULL\fR for \fIdmaereqp\fR if
no changes to the programming are required other than the address and count
values. It disables the channel prior to setup, and enables the channel before
returning. The \fBDMA\fR address and count are specified by passing
\fBddi_dmae_prog()\fR a \fBDMA\fR cookie.
Other \fBDMA\fR engine parameters are specified by the \fBDMA\fR engine request
structure passed in through \fIdmaereqp\fR. The fields of that structure are
documented in \fBddi_dmae_req\fR(9S).
.sp
.LP
Before using \fBddi_dmae_prog()\fR, you must allocate system \fBDMA\fR
resources using \fBDMA\fR setup functions such as \fBddi_dma_mem_alloc\fR(9F).
\fBddi_dma_addr_bind_handle\fR(9F) can then be used to retrieve a cookie which
contains the address and count. Then this cookie is passed to
\fBddi_dmae_prog()\fR.
.SS "\fBddi_dmae_disable()\fR"
The \fBddi_dmae_disable()\fR function disables the \fBDMA\fR channel so that it
no longer responds to a device's  \fBDMA\fR service requests.
.SS "\fBddi_dmae_enable()\fR"
The \fBddi_dmae_enable()\fR function enables the \fBDMA\fR channel for
operation. This may be used to re-enable the channel after a call to
\fBddi_dmae_disable()\fR. The channel is automatically enabled after successful
programming by \fBddi_dmae_prog()\fR.
.SS "\fBddi_dmae_stop()\fR"
The \fBddi_dmae_stop()\fR function disables the channel and terminates any
active operation.
.SS "\fBddi_dmae_getcnt()\fR"
The \fBddi_dmae_getcnt()\fR function examines the count register of the
\fBDMA\fR channel and sets \fI*countp\fR to the number of bytes remaining to be
transferred.  The channel is assumed to be stopped.
.SS "\fBddi_dmae_1stparty()\fR"
In the case of \fBISA\fR buses, \fBddi_dmae_1stparty()\fR configures a channel
in the system's \fBDMA\fR engine to operate in a ``slave'' (``cascade'') mode.
.sp
.LP
When operating in \fBddi_dmae_1stparty()\fR mode, the  \fBDMA\fR channel must
first be allocated using \fBddi_dmae_alloc()\fR and then configured using
\fBddi_dmae_1stparty()\fR. The driver then programs the device to perform the
I/O, including the necessary \fBDMA\fR address and count values obtained from
the \fBddi_dma_cookie\fR(9S).
.SS "\fBddi_dmae_getattr()\fR"
The \fBddi_dmae_getattr()\fR function fills in the \fBDMA\fR attribute
structure, pointed to by \fIattrp\fR, with the \fBDMA\fR attributes of the
system \fBDMA\fR engine. Drivers for devices that perform their own bus
mastering or use first-party \fBDMA\fR must create and initialize their own
\fBDMA\fR attribute structures; they should not use \fBddi_dmae_getattr()\fR.
The \fBDMA\fR attribute structure must be passed to the \fBDMA\fR resource
allocation functions to provide the information necessary to break the
\fBDMA\fR request into \fBDMA\fR windows and \fBDMA\fR cookies. See
\fBddi_dma_cookie_iter\fR(9F) and \fBddi_dma_getwin\fR(9F).
.SH RETURN VALUES
.ne 2
.na
\fB\fBDDI_SUCCESS\fR\fR
.ad
.RS 23n
Upon success, for all of these routines.
.RE

.sp
.ne 2
.na
\fB\fBDDI_FAILURE\fR\fR
.ad
.RS 23n
May be returned due to invalid arguments.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_NORESOURCES\fR\fR
.ad
.RS 23n
May be returned by \fBddi_dmae_alloc()\fR if the requested resources are not
available and the value of \fIdmae_waitfp\fR is not \fBDDI_DMA_SLEEP\fR.
.RE

.SH CONTEXT
If \fBddi_dmae_alloc()\fR is called from interrupt context, then its
\fIdmae_waitfp\fR argument and the callback function must not have the value
\fBDDI_DMA_SLEEP\fR. Otherwise, all these routines can be called from user,
interrupt, or kernel context.
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Architecture	x86
.TE

.SH SEE ALSO
.BR isa (5),
.BR attributes (7),
.BR ddi_dma_addr_bind_handle (9F),
.BR ddi_dma_buf_setup (9F),
.BR ddi_dma_cookie_iter (9F),
.BR ddi_dma_getwin (9F),
.BR ddi_dma_mem_alloc (9F),
.BR ddi_dma_attr (9S),
.BR ddi_dma_cookie (9S),
.BR ddi_dmae_req (9S)
